JPH03146414A - Production of porous binderless 3a-type zeolite formed body - Google Patents

Abstract

PURPOSE:To obtain the formed body useful as an adsorbent by calcining and foaming a formed body consisting of synthetic 4A-type zeolite, kaolinic clay and a foaming agent to convert the kaolinic clay into metakaoline, bringing the body into contact with aq. NaOH and then subjecting the body to K<+> ion exchange. CONSTITUTION:A formed body consisting of synthetic 4A-type zeolite, 20-30wt.% kaolinic clay based on the total amt. of the clay and zeolite and <=5wt.% foaming agent based on the total amt. of the zeolite and clay is calcined and foamed to convert the kaolinic clay into metakaoline. The formed body is then brought into contact with an aq. soln. contg. 1.0-3.0mol/l NaOH, and then subjected to ion exchange in a potassium-contg. soln. to produce the formed body. The formed body is of great use in adsorption, separation and refining, and exhibits an excellent performance as the adsorbent for the dehydration in the ethylene plant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a porous binderless 3A type zeolite molded body.

The binderless 3A type zeolite molded body is a useful adsorbent for adsorption separation and purification, and has excellent performance as an adsorbent for dehydration in ethylene plants, for example.

[Prior Art] JP-A-58-88120 discloses that a molded body consisting of 4A type zeolite powder and metakaolin as a clay binder is treated with an aqueous sodium hydroxide solution to convert the metakaolin into 4A type zeolite, and then As a method for improving the strength of a binderless type 3A zeolite molded body obtained by ion exchange treatment with a potassium ion-containing solution, the above molded body contains 40 to 60% by weight of metakaolin and is subjected to ion exchange treatment with a potassium ion-containing solution. A method of partial ion exchange with a calcium-containing solution prior to ion exchange is disclosed.

[Problems to be Solved by the Invention] This method uses metakaolin, that is, already sintered kaolin, as a binder, so the moldability is not very good; and there is no step of sintering the clay. The mechanical strength of the binderless 3A type zeolite molded product finally obtained remains low even after the calcium ion exchange treatment. If it is made porous, the solution containing sodium hydroxide and potassium ions can be applied to the center, but porous binderless 3
If such a method is applied to the production of a type A zeolite molded body, it will be possible to produce a type A zeolite molded body with even lower mechanical strength.

Furthermore, since a large amount of metakaolin is used, which inevitably introduces impurities such as amorphous silica, it is difficult to uniformly crystallize a product with a high zeolite content, including the scales and the center.

The purpose of the present invention is to create a binderless type 3A zeolite that is uniformly converted into zeolite, contains a higher purity of 3A type zeolite than those obtained by these conventional methods, and has excellent mechanical strength despite being porous. An object of the present invention is to provide a method for manufacturing a zeolite molded body.

[Means and effects for solving the problem] The use of clay as a factor to create a porous molded body with high zeolite content, excellent mechanical strength, and high adsorption capacity, and which is uniformly zeolized to the center. The type, mixing ratio of zeolite, clay, and blowing agent, concentration of aqueous sodium hydroxide solution, treatment temperature, firing conditions, etc. are considered.

The inventors of the present invention have conducted extensive studies on these factors, and as a result, have discovered a method that allows for the creation of molded bodies with improved performance.

The gist of the present invention is a synthetic 4A type zeolite,
Foaming by firing a molded body consisting of 20 to 30% by weight of kaolin-type clay based on the total amount of A-type zeolite and a blowing agent of 5% by weight or less based on the total of the synthetic 4A-type zeolite and the kaolin-type clay. The above-mentioned kaolin-type clay is converted into metakaolin, and the molded body is heated to a concentration of 1.0 to 1.0.
A method for producing a porous binderless 3A type zeolite molded body is provided, which comprises contacting with a 3.0 mol/j sodium hydroxide aqueous solution and then ion exchange treatment with a potassium ion-containing solution, the details of which will be described below.

The synthetic type 4A zeolite used in the present invention is synthesized by known methods, for example from sodium aluminate and sodium silicate.

This molded body is produced by adjusting the moisture content so that a mixture consisting of synthetic 4A type zeolite, kaolin clay, and a foaming agent in the above proportions can be molded, and in the case of extrusion molding, it is further lubricated to reduce the extrusion power. After adding the agent, it is kneaded until everything is homogeneous and then extrusion molded.

It can be manufactured by a pressure molding method such as a tableting method. That is, there is no limit to the shape of this molded body, and it may be granular, columnar, or spherical. In addition, this molded body is
In order to reduce the partial pressure of water vapor during the calcination described below and prevent hydrothermal deterioration of the zeolite crystal, the moisture content in the zeolite crystal is reduced to about 2
It is best to dry it until it reaches Q%.

If the amount of kaolin-type clay melon is less than 20 mm% of the total of the kaolin-type clay and the zeolite, it will not be possible to obtain a product with sufficient mechanical strength, while if it exceeds 30% by weight, the zeolite content will be high. It is difficult to obtain a molded body, and the performance of the product deteriorates.

If the amount of the blowing agent exceeds 5% by weight based on the total of the synthetic 4A type zeolite and the kaolin type clay, the porosity of the product will become too large and its strength will inevitably decrease, and the blowing agent may be an organic substance. In this case, the quality of the product will deteriorate due to the residue left during firing. However, if the amount is too small, it will become porous and insufficient, making it difficult to apply the sodium hydroxide aqueous solution or potassium ions to the center of the molded product. Good.

Naturally, this foaming agent must be one that decomposes and generates gas during firing, before the kaolin clay is converted to metakaolin and the molded body is solidified. Since the temperature at which kaolin clay starts sintering is about 550°C, handling of the blowing agent is facilitated by using a blowing agent with a decomposition temperature of 60 to 500°C. Examples of such materials include various polyethylenes, polyvinyl alcohols, and ammonium hydrogen carbonate.

In the present invention, first, a molded body consisting of synthetic 4A type zeolite, kaolin type clay, and a blowing agent in the above proportions,
Firing is performed in an atmosphere at 550 to 850°C, which is the firing temperature when synthesizing zeolite using kaolin as a raw material. It is sufficient that the firing time is 2 hours or more. By firing under the above conditions, the kaolin-type clay is sintered into highly reactive metakaolin, which strongly binds the zeolite crystals. In addition, the blowing agent is completely decomposed at the above firing temperature, and all of the lubricants used as molding aids are burned away, so the amount of impurities that cannot be converted into zeolite at this stage is relatively small in the present invention. There is only a small amount of amorphous silica accompanied by kaolin type clay.

As a result, it becomes a porous molded body, which has a great effect in uniformly converting the clay binder present inside the molded body into zeolite in the subsequent process of converting the clay binder into zeolite. .

Next, the fired molded body is humidified to a moisture content of 20% by weight or more, and preferably immersed in water to desorb the gases such as air adsorbed through its pores. Although this operation is not essential for the present invention, the molded body may crack during the subsequent treatment with an aqueous sodium hydroxide solution.
This is a preferable operation to eliminate the risk of cracking. The molded body that has been preferably humidified in this way is
Aging in a 1.0-3.0 mol/i aqueous solution of sodium hydroxide. The temperature for this aging may be in the range from the normal room temperature to about 40° C., and fine temperature control is not required. Furthermore, the aging time may be one hour or more, which is a short time. Next, the temperature of the sodium hydroxide aqueous solution in which the molded body is immersed is raised to 80° C. or higher and below the boiling point using a conventional method to completely convert the metakaolin in the molded body into 4A type zeolite. However, in consideration of industrial production, a relatively low temperature, that is, 80° C., is advantageous. Regarding the time, after 2 hours have elapsed after the temperature rise, metakaolin is almost completely converted to zeolite and the binderless molded product can be changed.

The reason why the clay binder can be converted into 4A type zeolite relatively easily is that the impurities are extremely reduced in the previous calcination, and almost all of the kaolin type clay in the molded body can be converted into zeolite. This indicates that it has been transferred to metakaolin, which is rich in sex.

The concentration of the above sodium hydroxide aqueous solution is 1.0 mol/
If it is lower than
This is undesirable because it tends to result in a molded product with a low pure zeolite content. On the other hand, if the concentration of the aqueous sodium hydroxide solution is higher than 3.0 mol/j, impurities such as sodalite will be produced, resulting in an extruded product having a low purity of type 4A zeolite, which is not preferable.

The porous extrusion molded body obtained by converting metakaolin into type 4A zeolite as described above is taken out from the aqueous sodium hydroxide solution, and excess sodium hydroxide is thoroughly washed with water.

Next, the porous binderless 4A zeolite molded body thus obtained is brought into contact with an aqueous solution containing potassium ions, that is, a potassium salt or hydroxide, and heated at a conventional temperature, that is, in the range from room temperature to about 40°C. Then, ion exchange is performed until the 4A type zeolite is converted to the 3A type zeolite. The time may be 3 hours or more, and it is a short time.

The molded body transferred to type 3A zeolite is taken out from the exchange solution, excess potassium ions adhering to the molded body are thoroughly washed with water, and dried.

In order to activate the obtained porous binderless type 3A zeolite, it is sufficient to calcinate the obtained porous binderless zeolite.

[Effects of the Invention] As is clear from the above description, according to the present invention, (1) a kaolin-type clay binder can be converted into 4A-type zeolite through simple steps and operations in a short time; It is possible to obtain a porous binderless zeolite molded body having a pore diameter of 3 angstroms, which (2) maintains excellent mechanical strength, and (3) is porous and contains a high zeolite purity.

[Example code] "Parts" in the following specific examples are by weight.

Example 1 100 parts of 4-part type synthetic zeolite powder was mixed with 25 parts of domestically produced kaolin type clay and 5 parts of polyethylene, and while adjusting the water content so that extrusion molding could be performed with low power, CMC ( 3 parts of (carboxymethyl cellulose) powder was added and mixed and kneaded in a muller mixer until uniform. Next, this kneaded material was extruded and molded into 3m/11 pellets using a Nisuke extruder,
After drying at 120°C, the particles were sized to have a length of 5 to 15 mm, and then fired in a Matsufuru furnace at a temperature of 650°C for 2 hours. After cooling, 100 g of the fired pellets were immersed in water to defoam, drained and reduced to a concentration of 2.0io1.
/i! The mixture was placed in a metal reaction vessel containing 500 ml of an aqueous sodium hydroxide solution, and aged at 40°C for 1 hour.
The clay binder was further left at 80° C. for 3 hours to convert into zeolite.

After thoroughly washing this product with water to remove excess sodium hydroxide, sodium ions were ion-exchanged with potassium ions using a potassium chloride aqueous solution having a concentration of 1.0 io1/i. This product was thoroughly washed with water, dried at 120°C, and activated by firing at 350°C for 1 hour.

Crystal analysis by X-ray diffraction showed that no other phases were present at all, indicating that the zeolite was a completely 3A type zeolite. The mechanical strength of this activated product was measured using a bookstore type hardness tester, and the pressure resistance was 10.4 kg. In addition, this activated product was placed in a desiccator with a relative humidity of 80% for 16 hours, and its pressure resistance was measured, and the result was 5.8 kg.
Met.

Further, the particle strength was measured by the method described in JIS K 1484, and the result was 0.36%, indicating that the water adsorption amount was 24.3%. These facts indicate that the molded body, which was almost completely converted into 4Au zeolite, was transformed into 3A type zeolite with a pore size of 3 angstroms by the ion exchange treatment.

Examples 2-6 The concentration of the sodium hydroxide aqueous solution is 1.0.1.5.

The same operations as in Example 1 were carried out except that the amounts were 2.0, 2.5 and 3.0 mol/b, to produce a molded body and to determine the amount of 7111j. The results are shown in Table 1.

Table 1 From these results, it can be seen that crystallization can be carried out with the concentration of the sodium hydroxide aqueous solution in the range of 1.0 to 3.0 Iiol/i.

Examples 7 to 11 Molded bodies were manufactured by performing exactly the same operations as in Example 2, except that the composition of the molded body was changed to 42.9 parts of domestically produced kaolin clay compared to the 4-part type synthetic zeolite powder (00 parts). and were measured.The results are shown in Table 2'.

Table 2 Example 12.13 The composition of the molded body was 100 parts of 4-part type synthetic zeolite powder, 25 parts of domestically produced kaolin-type clay, and 5 parts of polyvinyl alcohol (PVA) and ammonium hydrogen carbonate (ammonium carbonate) as blowing agents. Manufacturing and measurement were carried out in exactly the same manner as in Example 1, except that . The results are shown in Table 3.

Table 3 Example 14.15 Manufactured and produced in exactly the same manner as in Example 1 except that Joshia kaolin was used as the clay and the amounts were changed to 25 parts and 42.9 parts per 100 parts of 4-part type synthetic zeolite powder. I took measurements. The results are shown in Table 4.

Table 4 Comparative Example 1 A molded body was produced and processed in exactly the same manner as in Example 1 except that the composition of the molded body was changed to 67 parts of domestically produced kaolin clay for 100 parts of 4-part type synthetic zeolite powder. I took measurements.

The pressure resistance of the product under 80% relative humidity condition is 18.
5 kg, and the particle strength was 0.18%.

However, the amount of water adsorption was 21.7%, and the molded product had a low zeolite purity.

Comparative Example 2.3 The concentration of sodium hydroxide aqueous solution was 0.5 and 3.
A molded body was produced and the apl was determined by performing the same operations as in Example 1 except that the amount was 5n+ol/J.

The moisture adsorption capacity of the product is 22.6% and 22%, respectively.
．． The zeolite content was 9%, indicating that the molded product had a low zeolite purity.

Comparative Example 4 A molded article was produced and measured in the same manner as in Example 1 except that polyethylene was not used.

The pressure resistance of the product is 5.6 kg, the particle strength is 0.32%,
The amount of water adsorption was 23.1%.

Claims (2)

[Claims] (1) Synthetic 4A zeolite, 20 to 30% by weight of kaolin clay based on the total of the synthetic 4A zeolite, and foaming of 5% by weight or less based on the total of the synthetic 4A zeolite and kaolin clay. A molded body made of the agent is fired and foamed, and the above-mentioned kaolin type clay is converted to metakaolin, and the molded body is heated to a concentration of 1.0 to 3.0 mol/
1. A method for producing a porous binderless 3A type zeolite molded body, which comprises bringing it into contact with an aqueous sodium hydroxide solution of 100 ml, followed by ion exchange treatment with a potassium ion-containing solution. (2) The method according to claim (1), wherein the blowing agent is polyethylene, polyvinyl alcohol, or ammonium hydrogen carbonate.